The present invention relates to the structure of a door mirror of a vehicle.
A door mirror is attached in front of a front door of a vehicle. When the vehicle runs, wind blows against the vehicle body and flows around the door mirror. The wind flowing around the door mirror is a mixture of winds including wind hitting a front glass from ahead and flowing toward the door mirror, wind hitting the door mirror straightly from ahead, wind rising from a tire and hitting the door mirror, and so on. The wind hitting the door mirror is dispersed by the door mirror and separated from the door mirror to flow rearward. On this occasion, in the vicinity of a housing of the door mirror, the dispersed wind is split into an air current passing between the housing and a side surface of the vehicle body, an air current passing through an upper side of the housing, an air current passing through a side (vehicle-width-direction outer side) of the housing, and an air current passing through a lower side of the housing. Then, the split air currents flow rearward.
As described above, the complex air currents occur in the vicinity of the door mirror when the vehicle runs. Accordingly, the change of sound pressure of wind noise caused by turbulence of the air currents may be sensed as noisy sound by a passenger. In addition, the wind (air current) passing between the housing and the side surface of the vehicle body flows toward the vicinity of the door glass so that sound generated by the flowing of the wind may be heard as noise by the passenger. In addition, the wind (air current) having been separated from the door mirror may generate a vortex, which may hit the door glass to be heard as noise. There have been proposed techniques aiming at reducing aerodynamic noise which is caused by the flows of winds generated thus in the vicinity of a door mirror when the vehicle is running.
For example, JP-A-2007-137130 discloses a door mirror having a protrusion. The protrusion is formed in the surface of the vicinity of a vehicle rear side edge portion of an attachment portion serving as a base portion fixed to a vehicle body, so as to extend along the side edge portion. This technique suggests that a turbulent flow occurring due to wind blowing between a housing and the attachment portion of the door mirror is separated from the vehicle body (door glass surface) and allowed to flow rearward by the protrusion formed in the side edge portion, so that the sound of the wind as noise can be reduced.
In addition, Japanese Patent No. 4240383 discloses a door mirror having a configuration in which a plurality of protrusions are arranged side by side only in an outer side surface of a housing not facing a vehicle, so that an air current flowing along the outer side surface can flow among the protrusions to be rectified. This technique suggests that the air current flowing toward the outer side surface of the door mirror can be rectified by the protrusions formed in the outer side surface to thereby prevent fluctuation in pressure and vibration in the mirror caused by a separation vortex.
Wind from any direction gathers on the lower side of the housing among the flows of winds in the vicinity of the door mirror of the vehicle. Accordingly, the flow velocity, the flow rate or the direction is disturbed easily so that aerodynamic noise can be generated due to fluctuation in the flow velocity, the flow rate or the direction. The aforementioned JP-A-2007-137130 and Japanese Patent No. 4240383 disclose techniques for rectifying the wind (air current) flowing between the housing of the door mirror and the vehicle body and the wind (air current) flowing along the outer side surface of the housing. However, the aforementioned JP-A-2007-137130 and Japanese Patent No. 4240383 are not focused on the wind passing through the lower side of the housing of the door mirror.